Effects of sunlight exclusion on leaf gas exchange, berry composition, and wine flavour profile of Cabernet-Sauvignon from the foot of the north side of Mount Tianshan and a semi-arid continental climate

Abstract

Canopy shading is a widely used viticultural strategy for mitigating early grape berry ripening caused by global warming. In this study, we covered half of the canopy with a black shade cloth from the pea-size stage to harvest. In the fruit zone, canopy shade treatment (ST) reduced daily average solar radiation by about 74.6 % compared to the untreated control (UC), and significantly reduced daily average temperature. ST leaves were found to have lower net assimilation rates and higher internal CO2 concentration than in UC, which resulted in reduced yield, bunch weight, cane starch and berry total soluble solids. A delayed development stage was found in ST berries which had lower pH and higher titratable acid than UC. ST increased both berry and wine anthocyanin concentration while significantly decreasing flavonol concentration. ST wines had higher concentrations of a number of ester compounds and β-damascenone than UC wines, thus significantly enhancing the floral and fruity aroma of ST wines. Higher C6/C9 and fatty acids concentrations in ST berries may have caused higher ester concentrations in ST wines. The results showed significant effects on metabolites in berries and wines caused by canopy shade.